Re-wrap the text at 80 columns after fixing the indent in the prior commit.

[FreeBSD/FreeBSD.git] / UPDATING

 Updating Information for FreeBSD current users.

This file is maintained and copyrighted by M. Warner Losh <imp@freebsd.org>.
See end of file for further details.  For commonly done items, please see the
COMMON ITEMS: section later in the file.  These instructions assume that you
basically know what you are doing.  If not, then please consult the FreeBSD
handbook:

    https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html

Items affecting the ports and packages system can be found in
/usr/ports/UPDATING.  Please read that file before running portupgrade.

NOTE TO PEOPLE WHO THINK THAT FreeBSD 13.x IS SLOW:
        FreeBSD 13.x has many debugging features turned on, in both the kernel
        and userland.  These features attempt to detect incorrect use of
        system primitives, and encourage loud failure through extra sanity
        checking and fail stop semantics.  They also substantially impact
        system performance.  If you want to do performance measurement,
        benchmarking, and optimization, you'll want to turn them off.  This
        includes various WITNESS- related kernel options, INVARIANTS, malloc
        debugging flags in userland, and various verbose features in the
        kernel.  Many developers choose to disable these features on build
        machines to maximize performance.  (To completely disable malloc
        debugging, define MALLOC_PRODUCTION in /etc/make.conf, or to merely
        disable the most expensive debugging functionality run
        "ln -s 'abort:false,junk:false' /etc/malloc.conf".)

20190713:
        Default permissions on the /var/account/acct file (and copies of it 
        rotated by periodic daily scripts) are changed from 0644 to 0640 
        because the file contains sensitive information that should not be 
        world-readable.  If the /var/account directory must be created by 
        rc.d/accounting, the mode used is now 0750.  Admins who use the 
        accounting feature are encouraged to change the mode of an existing 
        /var/account directory to 0750 or 0700.  

20190620:
        Entropy collection and the /dev/random device are no longer optional
        components.  The "device random" option has been removed.
        Implementations of distilling algorithms can still be made loadable
        with "options RANDOM_LOADABLE" (e.g., random_fortuna.ko).

20190612:
        Clang, llvm, lld, lldb, compiler-rt, libc++, libunwind and openmp have
        been upgraded to 8.0.1.  Please see the 20141231 entry below for
        information about prerequisites and upgrading, if you are not already
        using clang 3.5.0 or higher.

20190608:
        A fix was applied to i386 kernel modules to avoid panics with
        dpcpu or vnet.  Users need to recompile i386 kernel modules
        having pcpu or vnet sections or they will refuse to load.

20190513:
        User-wired pages now have their own counter,
        vm.stats.vm.v_user_wire_count.  The vm.max_wired sysctl was renamed
        to vm.max_user_wired and changed from an unsigned int to an unsigned
        long.  bhyve VMs wired with the -S are now subject to the user
        wiring limit; the vm.max_user_wired sysctl may need to be tuned to
        avoid running into the limit.

20190507:
        The IPSEC option has been removed from GENERIC.  Users requiring
        ipsec(4) must now load the ipsec(4) kernel module.

20190507:
        The tap(4) driver has been folded into tun(4), and the module has been
        renamed to tuntap.  You should update any kld_load="if_tap" or
        kld_load="if_tun" entries in /etc/rc.conf, if_tap_load="YES" or
        if_tun_load="YES" entries in /boot/loader.conf to load the if_tuntap
        module instead, and "device tap" or "device tun" entries in kernel
        config files to select the tuntap device instead.

20190418:
        The following knobs have been added related to tradeoffs between
        safe use of the random device and availability in the absence of
        entropy:

        kern.random.initial_seeding.bypass_before_seeding: tunable; set
        non-zero to bypass the random device prior to seeding, or zero to
        block random requests until the random device is initially seeded.
        For now, set to 1 (unsafe) by default to restore pre-r346250 boot
        availability properties.

        kern.random.initial_seeding.read_random_bypassed_before_seeding:
        read-only diagnostic sysctl that is set when bypass is enabled and
        read_random(9) is bypassed, to enable programmatic handling of this
        initial condition, if desired.

        kern.random.initial_seeding.arc4random_bypassed_before_seeding:
        Similar to the above, but for for arc4random(9) initial seeding.

        kern.random.initial_seeding.disable_bypass_warnings: tunable; set
        non-zero to disable warnings in dmesg when the same conditions are
        met as for the diagnostic sysctls above.  Defaults to zero, i.e.,
        produce warnings in dmesg when the conditions are met.

20190416:
        The loadable random module KPI has changed; the random_infra_init()
        routine now requires a 3rd function pointer for a bool (*)(void)
        method that returns true if the random device is seeded (and
        therefore unblocked).

20190404:
        r345895 reverts r320698. This implies that an nfsuserd(8) daemon
        built from head sources between r320757 (July 6, 2017) and
        r338192 (Aug. 22, 2018) will not work unless the "-use-udpsock"
        is added to the command line.
        nfsuserd daemons built from head sources that are post-r338192 are
        not affected and should continue to work.

20190320:
        The fuse(4) module has been renamed to fusefs(4) for consistency with
        other filesystems.  You should update any kld_load="fuse" entries in
        /etc/rc.conf, fuse_load="YES" entries in /boot/loader.conf, and
        "options FUSE" entries in kernel config files.

20190304:
        Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to
        8.0.0.  Please see the 20141231 entry below for information about
        prerequisites and upgrading, if you are not already using clang 3.5.0
        or higher.

20190226:
        geom_uzip(4) depends on the new module xz.  If geom_uzip is statically
        compiled into your custom kernel, add 'device xz' statement to the
        kernel config.

20190219:
        drm and drm2 have been removed from the tree. Please see
        https://wiki.freebsd.org/Graphics for the latest information on
        migrating to the drm ports.

20190131:
        Iflib is no longer unconditionally compiled into the kernel.  Drivers
        using iflib and statically compiled into the kernel, now require
        the 'device iflib' config option.  For the same drivers loaded as
        modules on kernels not having 'device iflib', the iflib.ko module
        is loaded automatically.

20190125:
        The IEEE80211_AMPDU_AGE and AH_SUPPORT_AR5416 kernel configuration
        options no longer exist since r343219 and r343427 respectively;
        nothing uses them, so they should be just removed from custom
        kernel config files.

20181230:
        r342635 changes the way efibootmgr(8) works by requiring users to add
        the -b (bootnum) parameter for commands where the bootnum was previously
        specified with each option. For example 'efibootmgr -B 0001' is now
        'efibootmgr -B -b 0001'.

20181220:
        r342286 modifies the NFSv4 server so that it obeys vfs.nfsd.nfs_privport
        in the same as it is applied to NFSv2 and 3.  This implies that NFSv4
        servers that have vfs.nfsd.nfs_privport set will only allow mounts
        from clients using a reserved port#. Since both the FreeBSD and Linux
        NFSv4 clients use reserved port#s by default, this should not affect
        most NFSv4 mounts.

20181219:
        The XLP config has been removed. We can't support 64-bit atomics in this
        kernel because it is running in 32-bit mode. XLP users must transition
        to running a 64-bit kernel (XLP64 or XLPN32).

        The mips GXEMUL support has been removed from FreeBSD. MALTA* + qemu is
        the preferred emulator today and we don't need two different ones.

        The old sibyte / swarm / Broadcom BCM1250 support has been
        removed from the mips port.

20181211:
        Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to
        7.0.1.  Please see the 20141231 entry below for information about
        prerequisites and upgrading, if you are not already using clang 3.5.0
        or higher.

20181211:
        Remove the timed and netdate programs from the base tree.  Setting
        the time with these daemons has been obsolete for over a decade.

20181126:
        On amd64, arm64 and armv7 (architectures that install LLVM's ld.lld
        linker as /usr/bin/ld) GNU ld is no longer installed as ld.bfd, as
        it produces broken binaries when ifuncs are in use.  Users needing
        GNU ld should install the binutils port or package.

20181123:
        The BSD crtbegin and crtend code has been enabled by default. It has
        had extensive testing on amd64, arm64, and i386. It can be disabled
        by building a world with -DWITHOUT_BSD_CRTBEGIN.

20181115:
        The set of CTM commands (ctm, ctm_smail, ctm_rmail, ctm_dequeue)
        has been converted to a port (misc/ctm) and will be removed from
        FreeBSD-13.  It is available as a package (ctm) for all supported
        FreeBSD versions.

20181110:
        The default newsyslog.conf(5) file has been changed to only include
        files in /etc/newsyslog.conf.d/ and /usr/local/etc/newsyslog.conf.d/ if
        the filenames end in '.conf' and do not begin with a '.'.

        You should check the configuration files in these two directories match
        this naming convention. You can verify which configuration files are
        being included using the command:
                $ newsyslog -Nrv

20181015:
        Ports for the DRM modules have been simplified. Now, amd64 users should
        just install the drm-kmod port. All others should install
        drm-legacy-kmod.

        Graphics hardware that's newer than about 2010 usually works with
        drm-kmod.  For hardware older than 2013, however, some users will need
        to use drm-legacy-kmod if drm-kmod doesn't work for them. Hardware older
        than 2008 usually only works in drm-legacy-kmod. The graphics team can
        only commit to hardware made since 2013 due to the complexity of the
        market and difficulty to test all the older cards effectively. If you
        have hardware supported by drm-kmod, you are strongly encouraged to use
        that as you will get better support.

        Other than KPI chasing, drm-legacy-kmod will not be updated. As outlined
        elsewhere, the drm and drm2 modules will be eliminated from the src base
        soon (with a limited exception for arm). Please update to the package
        asap and report any issues to x11@freebsd.org.

        Generally, anybody using the drm*-kmod packages should add
        WITHOUT_DRM_MODULE=t and WITHOUT_DRM2_MODULE=t to avoid nasty
        cross-threading surprises, especially with automatic driver
        loading from X11 startup. These will become the defaults in 13-current
        shortly.

20181012:
        The ixlv(4) driver has been renamed to iavf(4).  As a consequence,
        custom kernel and module loading configuration files must be updated
        accordingly.  Moreover, interfaces previous presented as ixlvN to the
        system are now exposed as iavfN and network configuration files must
        be adjusted as necessary.

20181009:
        OpenSSL has been updated to version 1.1.1.  This update included
        additional various API changes throughout the base system.  It is
        important to rebuild third-party software after upgrading.  The value
        of __FreeBSD_version has been bumped accordingly.

20181006:
        The legacy DRM modules and drivers have now been added to the loader's
        module blacklist, in favor of loading them with kld_list in rc.conf(5).
        The module blacklist may be overridden with the loader.conf(5)
        'module_blacklist' variable, but loading them via rc.conf(5) is strongly
        encouraged.

20181002:
        The cam(4) based nda(4) driver will be used over nvd(4) by default on
        powerpc64. You may set 'options NVME_USE_NVD=1' in your kernel conf or
        loader tunable 'hw.nvme.use_nvd=1' if you wish to use the existing
        driver.  Make sure to edit /boot/etc/kboot.conf and fstab to use the
        nda device name.

20180913:
        Reproducible build mode is now on by default, in preparation for
        FreeBSD 12.0.  This eliminates build metadata such as the user,
        host, and time from the kernel (and uname), unless the working tree
        corresponds to a modified checkout from a version control system.
        The previous behavior can be obtained by setting the /etc/src.conf
        knob WITHOUT_REPRODUCIBLE_BUILD.

20180826:
        The Yarrow CSPRNG has been removed from the kernel as it has not been
        supported by its designers since at least 2003. Fortuna has been the
        default since FreeBSD-11.

20180822:
        devctl freeze/thaw have gone into the tree, the rc scripts have been
        updated to use them and devmatch has been changed.  You should update
        kernel, userland and rc scripts all at the same time.

20180818:
        The default interpreter has been switched from 4th to Lua.
        LOADER_DEFAULT_INTERP, documented in build(7), will override the default
        interpreter.  If you have custom FORTH code you will need to set
        LOADER_DEFAULT_INTERP=4th (valid values are 4th, lua or simp) in
        src.conf for the build.  This will create default hard links between
        loader and loader_4th instead of loader and loader_lua, the new default.
        If you are using UEFI it will create the proper hard link to loader.efi.

        bhyve uses userboot.so. It remains 4th-only until some issues are solved
        regarding coexisting with multiple versions of FreeBSD are resolved.

20180815:
        ls(1) now respects the COLORTERM environment variable used in other
        systems and software to indicate that a colored terminal is both
        supported and desired.  If ls(1) is suddenly emitting colors, they may
        be disabled again by either removing the unwanted COLORTERM from your
        environment, or using `ls --color=never`.  The ls(1) specific CLICOLOR
        may not be observed in a future release.

20180808:
        The default pager for most commands has been changed to "less".  To
        restore the old behavior, set PAGER="more" and MANPAGER="more -s" in
        your environment.

20180731:
        The jedec_ts(4) driver has been removed. A superset of its functionality
        is available in the jedec_dimm(4) driver, and the manpage for that
        driver includes migration instructions. If you have "device jedec_ts"
        in your kernel configuration file, it must be removed.

20180730:
        amd64/GENERIC now has EFI runtime services, EFIRT, enabled by default.
        This should have no effect if the kernel is booted via BIOS/legacy boot.
        EFIRT may be disabled via a loader tunable, efi.rt.disabled, if a system
        has a buggy firmware that prevents a successful boot due to use of
        runtime services.

20180727:
        Atmel AT91RM9200 and AT91SAM9, Cavium CNS 11xx and XScale
        support has been removed from the tree. These ports were
        obsolete and/or known to be broken for many years.

20180723:
        loader.efi has been augmented to participate more fully in the
        UEFI boot manager protocol. loader.efi will now look at the
        BootXXXX environment variable to determine if a specific kernel
        or root partition was specified. XXXX is derived from BootCurrent.
        efibootmgr(8) manages these standard UEFI variables.

20180720:
        zfsloader's functionality has now been folded into loader.
        zfsloader is no longer necessary once you've updated your
        boot blocks. For a transition period, we will install a
        hardlink for zfsloader to loader to allow a smooth transition
        until the boot blocks can be updated (hard link because old
        zfs boot blocks don't understand symlinks).

20180719:
        ARM64 now have efifb support, if you want to have serial console
        on your arm64 board when an screen is connected and the bootloader
        setup a frame buffer for us to use, just add :
        boot_serial=YES
        boot_multicons=YES
        in /boot/loader.conf
        For Raspberry Pi 3 (RPI) users, this is needed even if you don't have
        an screen connected as the firmware will setup a frame buffer are that
        u-boot will expose as an EFI frame buffer.

20180719:
        New uid:gid added, ntpd:ntpd (123:123).  Be sure to run mergemaster
        or take steps to update /etc/passwd before doing installworld on
        existing systems.  Do not skip the "mergemaster -Fp" step before
        installworld, as described in the update procedures near the bottom
        of this document.  Also, rc.d/ntpd now starts ntpd(8) as user ntpd
        if the new mac_ntpd(4) policy is available, unless ntpd_flags or
        the ntp config file contain options that change file/dir locations.
        When such options (e.g., "statsdir" or "crypto") are used, ntpd can
        still be run as non-root by setting ntpd_user=ntpd in rc.conf, after
        taking steps to ensure that all required files/dirs are accessible
        by the ntpd user.

20180717:
        Big endian arm support has been removed.

20180711:
        The static environment setup in kernel configs is no longer mutually
        exclusive with the loader(8) environment by default.  In order to
        restore the previous default behavior of disabling the loader(8)
        environment if a static environment is present, you must specify
        loader_env.disabled=1 in the static environment.

20180705:
        The ABI of syscalls used by management tools like sockstat and
        netstat has been broken to allow 32-bit binaries to work on
        64-bit kernels without modification.  These programs will need
        to match the kernel in order to function.  External programs may
        require minor modifications to accommodate a change of type in
        structures from pointers to 64-bit virtual addresses.

20180702:
        On i386 and amd64 atomics are now inlined. Out of tree modules using
        atomics will need to be rebuilt.

20180701:
        The '%I' format in the kern.corefile sysctl limits the number of
        core files that a process can generate to the number stored in the
        debug.ncores sysctl. The '%I' format is replaced by the single digit
        index. Previously, if all indexes were taken the kernel would overwrite
        only a core file with the highest index in a filename.
        Currently the system will create a new core file if there is a free
        index or if all slots are taken it will overwrite the oldest one.

20180630:
        Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to
        6.0.1.  Please see the 20141231 entry below for information about
        prerequisites and upgrading, if you are not already using clang 3.5.0
        or higher.

20180628:
        r335753 introduced a new quoting method. However, etc/devd/devmatch.conf
        needed to be changed to work with it. This change was made with r335763
        and requires a mergemaster / etcupdate / etc to update the installed
        file.

20180612:
        r334930 changed the interface between the NFS modules, so they all
        need to be rebuilt.  r335018 did a __FreeBSD_version bump for this.

20180530:
        As of r334391 lld is the default amd64 system linker; it is installed
        as /usr/bin/ld.  Kernel build workarounds (see 20180510 entry) are no
        longer necessary.

20180530:
        The kernel / userland interface for devinfo changed, so you'll
        need a new kernel and userland as a pair for it to work (rebuilding
        lib/libdevinfo is all that's required). devinfo and devmatch will
        not work, but everything else will when there's a mismatch.

20180523:
        The on-disk format for hwpmc callchain records has changed to include
        threadid corresponding to a given record. This changes the field offsets
        and thus requires that libpmcstat be rebuilt before using a kernel
        later than r334108.

20180517:
        The vxge(4) driver has been removed.  This driver was introduced into
        HEAD one week before the Exar left the Ethernet market and is not
        known to be used.  If you have device vxge in your kernel config file
        it must be removed.

20180510:
        The amd64 kernel now requires a ld that supports ifunc to produce a
        working kernel, either lld or a newer binutils. lld is built by default
        on amd64, and the 'buildkernel' target uses it automatically. However,
        it is not the default linker, so building the kernel the traditional
        way requires LD=ld.lld on the command line (or LD=/usr/local/bin/ld for
        binutils port/package). lld will soon be default, and this requirement
        will go away.

        NOTE: As of r334391 lld is the default system linker on amd64, and no
        workaround is necessary.

20180508:
        The nxge(4) driver has been removed.  This driver was for PCI-X 10g
        cards made by s2io/Neterion.  The company was acquired by Exar and
        no longer sells or supports Ethernet products.  If you have device
        nxge in your kernel config file it must be removed.

20180504:
        The tz database (tzdb) has been updated to 2018e.  This version more
        correctly models time stamps in time zones with negative DST such as
        Europe/Dublin (from 1971 on), Europe/Prague (1946/7), and
        Africa/Windhoek (1994/2017).  This does not affect the UT offsets, only
        time zone abbreviations and the tm_isdst flag.

20180502:
        The ixgb(4) driver has been removed.  This driver was for an early and
        uncommon legacy PCI 10GbE for a single ASIC, Intel 82597EX. Intel
        quickly shifted to the long lived ixgbe family.  If you have device
        ixgb in your kernel config file it must be removed.

20180501:
        The lmc(4) driver has been removed.  This was a WAN interface
        card that was already reportedly rare in 2003, and had an ambiguous
        license.  If you have device lmc in your kernel config file it must
        be removed.

20180413:
        Support for Arcnet networks has been removed.  If you have device
        arcnet or device cm in your kernel config file they must be
        removed.

20180411:
        Support for FDDI networks has been removed.  If you have device
        fddi or device fpa in your kernel config file they must be
        removed.

20180406:
        In addition to supporting RFC 3164 formatted messages, the
        syslogd(8) service is now capable of parsing RFC 5424 formatted
        log messages. The main benefit of using RFC 5424 is that clients
        may now send log messages with timestamps containing year numbers,
        microseconds and time zone offsets.

        Similarly, the syslog(3) C library function has been altered to
        send RFC 5424 formatted messages to the local system logging
        daemon. On systems using syslogd(8), this change should have no
        negative impact, as long as syslogd(8) and the C library are
        updated at the same time. On systems using a different system
        logging daemon, it may be necessary to make configuration
        adjustments, depending on the software used.

        When using syslog-ng, add the 'syslog-protocol' flag to local
        input sources to enable parsing of RFC 5424 formatted messages:

                source src {
                        unix-dgram("/var/run/log" flags(syslog-protocol));
                }

        When using rsyslog, disable the 'SysSock.UseSpecialParser' option
        of the 'imuxsock' module to let messages be processed by the
        regular RFC 3164/5424 parsing pipeline:

                module(load="imuxsock" SysSock.UseSpecialParser="off")

        Do note that these changes only affect communication between local
        applications and syslogd(8). The format that syslogd(8) uses to
        store messages on disk or forward messages to other systems
        remains unchanged. syslogd(8) still uses RFC 3164 for these
        purposes. Options to customize this behaviour will be added in the
        future. Utilities that process log files stored in /var/log are
        thus expected to continue to function as before.

        __FreeBSD_version has been incremented to 1200061 to denote this
        change.

20180328:
        Support for token ring networks has been removed. If you
        have "device token" in your kernel config you should remove
        it. No device drivers supported token ring.

20180323:
        makefs was modified to be able to tag ISO9660 El Torito boot catalog
        entries as EFI instead of overloading the i386 tag as done previously.
        The amd64 mkisoimages.sh script used to build amd64 ISO images for
        release was updated to use this. This may mean that makefs must be
        updated before "make cdrom" can be run in the release directory. This
        should be as simple as:

                $ cd $SRCDIR/usr.sbin/makefs
                $ make depend all install

20180212:
        FreeBSD boot loader enhanced with Lua scripting. It's purely opt-in for
        now by building WITH_LOADER_LUA and WITHOUT_FORTH in /etc/src.conf.
        Co-existence for the transition period will come shortly. Booting is a
        complex environment and test coverage for Lua-enabled loaders has been
        thin, so it would be prudent to assume it might not work and make
        provisions for backup boot methods.

20180211:
        devmatch functionality has been turned on in devd. It will automatically
        load drivers for unattached devices. This may cause unexpected drivers
        to be loaded. Please report any problems to current@ and
        imp@freebsd.org.

20180114:
        Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to
        6.0.0.  Please see the 20141231 entry below for information about
        prerequisites and upgrading, if you are not already using clang 3.5.0
        or higher.

20180110:
        LLVM's lld linker is now used as the FreeBSD/amd64 bootstrap linker.
        This means it is used to link the kernel and userland libraries and
        executables, but is not yet installed as /usr/bin/ld by default.

        To revert to ld.bfd as the bootstrap linker, in /etc/src.conf set
        WITHOUT_LLD_BOOTSTRAP=yes

20180110:
        On i386, pmtimer has been removed. Its functionality has been folded
        into apm. It was a no-op on ACPI in current for a while now (but was
        still needed on i386 in FreeBSD 11 and earlier). Users may need to
        remove it from kernel config files.

20180104:
        The use of RSS hash from the network card aka flowid has been
        disabled by default for lagg(4) as it's currently incompatible with
        the lacp and loadbalance protocols.

        This can be re-enabled by setting the following in loader.conf:
        net.link.lagg.default_use_flowid="1"

20180102:
        The SW_WATCHDOG option is no longer necessary to enable the
        hardclock-based software watchdog if no hardware watchdog is
        configured. As before, SW_WATCHDOG will cause the software
        watchdog to be enabled even if a hardware watchdog is configured.

20171215:
        r326887 fixes the issue described in the 20171214 UPDATING entry.
        r326888 flips the switch back to building GELI support always.

20171214:
        r362593 broke ZFS + GELI support for reasons unknown. However,
        it also broke ZFS support generally, so GELI has been turned off
        by default as the lesser evil in r326857. If you boot off ZFS and/or
        GELI, it might not be a good time to update.

20171125:
        PowerPC users must update loader(8) by rebuilding world before
        installing a new kernel, as the protocol connecting them has
        changed. Without the update, loader metadata will not be passed
        successfully to the kernel and users will have to enter their
        root partition at the kernel mountroot prompt to continue booting.
        Newer versions of loader can boot old kernels without issue.

20171110:
        The LOADER_FIREWIRE_SUPPORT build variable as been renamed to
        WITH/OUT_LOADER_FIREWIRE. LOADER_{NO_,}GELI_SUPPORT has been renamed
        to WITH/OUT_LOADER_GELI.

20171106:
        The naive and non-compliant support of posix_fallocate(2) in ZFS
        has been removed as of r325320.  The system call now returns EINVAL
        when used on a ZFS file.  Although the new behavior complies with the
        standard, some consumers are not prepared to cope with it.
        One known victim is lld prior to r325420.

20171102:
        Building in a FreeBSD src checkout will automatically create object
        directories now rather than store files in the current directory if
        'make obj' was not ran.  Calling 'make obj' is no longer necessary.
        This feature can be disabled by setting WITHOUT_AUTO_OBJ=yes in
        /etc/src-env.conf (not /etc/src.conf), or passing the option in the
        environment.

20171101:
        The default MAKEOBJDIR has changed from /usr/obj/<srcdir> for native
        builds, and /usr/obj/<arch>/<srcdir> for cross-builds, to a unified
        /usr/obj/<srcdir>/<arch>.  This behavior can be changed to the old
        format by setting WITHOUT_UNIFIED_OBJDIR=yes in /etc/src-env.conf,
        the environment, or with -DWITHOUT_UNIFIED_OBJDIR when building.
        The UNIFIED_OBJDIR option is a transitional feature that will be
        removed for 12.0 release; please migrate to the new format for any
        tools by looking up the OBJDIR used by 'make -V .OBJDIR' means rather
        than hardcoding paths.

20171028:
        The native-xtools target no longer installs the files by default to the
        OBJDIR.  Use the native-xtools-install target with a DESTDIR to install
        to ${DESTDIR}/${NXTP} where NXTP defaults to /nxb-bin.

20171021:
        As part of the boot loader infrastructure cleanup, LOADER_*_SUPPORT
        options are changing from controlling the build if defined / undefined
        to controlling the build with explicit 'yes' or 'no' values. They will
        shift to WITH/WITHOUT options to match other options in the system.

20171010:
        libstand has turned into a private library for sys/boot use only.
        It is no longer supported as a public interface outside of sys/boot.

20171005:
        The arm port has split armv6 into armv6 and armv7. armv7 is now
        a valid TARGET_ARCH/MACHINE_ARCH setting. If you have an armv7 system
        and are running a kernel from before r324363, you will need to add
        MACHINE_ARCH=armv7 to 'make buildworld' to do a native build.

20171003:
        When building multiple kernels using KERNCONF, non-existent KERNCONF
        files will produce an error and buildkernel will fail. Previously
        missing KERNCONF files silently failed giving no indication as to
        why, only to subsequently discover during installkernel that the
        desired kernel was never built in the first place.

20170912:
        The default serial number format for CTL LUNs has changed.  This will
        affect users who use /dev/diskid/* device nodes, or whose FibreChannel
        or iSCSI clients care about their LUNs' serial numbers.  Users who
        require serial number stability should hardcode serial numbers in
        /etc/ctl.conf .

20170912:
        For 32-bit arm compiled for hard-float support, soft-floating point
        binaries now always get their shared libraries from
        LD_SOFT_LIBRARY_PATH (in the past, this was only used if
        /usr/libsoft also existed). Only users with a hard-float ld.so, but
        soft-float everything else should be affected.

20170826:
        The geli password typed at boot is now hidden.  To restore the previous
        behavior, see geli(8) for configuration options.

20170825:
        Move PMTUD blackhole counters to TCPSTATS and remove them from bare
        sysctl values.  Minor nit, but requires a rebuild of both world/kernel
        to complete.

20170814:
        "make check" behavior (made in ^/head@r295380) has been changed to
        execute from a limited sandbox, as opposed to executing from
        ${TESTSDIR}.

        Behavioral changes:
        - The "beforecheck" and "aftercheck" targets are now specified.
        - ${CHECKDIR} (added in commit noted above) has been removed.
        - Legacy behavior can be enabled by setting
          WITHOUT_MAKE_CHECK_USE_SANDBOX in src.conf(5) or the environment.

        If the limited sandbox mode is enabled, "make check" will execute
        "make distribution", then install, execute the tests, and clean up the
        sandbox if successful.

        The "make distribution" and "make install" targets are typically run as
        root to set appropriate permissions and ownership at installation time.
        The end-user should set "WITH_INSTALL_AS_USER" in src.conf(5) or the
        environment if executing "make check" with limited sandbox mode using
        an unprivileged user.

20170808:
        Since the switch to GPT disk labels, fsck for UFS/FFS has been
        unable to automatically find alternate superblocks. As of r322297,
        the information needed to find alternate superblocks has been
        moved to the end of the area reserved for the boot block.
        Filesystems created with a newfs of this vintage or later
        will create the recovery information. If you have a filesystem
        created prior to this change and wish to have a recovery block
        created for your filesystem, you can do so by running fsck in
        foreground mode (i.e., do not use the -p or -y options). As it
        starts, fsck will ask ``SAVE DATA TO FIND ALTERNATE SUPERBLOCKS''
        to which you should answer yes.

20170728:
        As of r321665, an NFSv4 server configuration that services
        Kerberos mounts or clients that do not support the uid/gid in
        owner/owner_group string capability, must explicitly enable
        the nfsuserd daemon by adding nfsuserd_enable="YES" to the
        machine's /etc/rc.conf file.

20170722:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 5.0.0.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20170701:
        WITHOUT_RCMDS is now the default. Set WITH_RCMDS if you need the
        r-commands (rlogin, rsh, etc.) to be built with the base system.

20170625:
        The FreeBSD/powerpc platform now uses a 64-bit type for time_t.  This is
        a very major ABI incompatible change, so users of FreeBSD/powerpc must
        be careful when performing source upgrades.  It is best to run
        'make installworld' from an alternate root system, either a live
        CD/memory stick, or a temporary root partition.  Additionally, all ports
        must be recompiled.  powerpc64 is largely unaffected, except in the case
        of 32-bit compatibility.  All 32-bit binaries will be affected.

20170623:
        Forward compatibility for the "ino64" project have been committed. This
        will allow most new binaries to run on older kernels in a limited
        fashion.  This prevents many of the common foot-shooting actions in the
        upgrade as well as the limited ability to roll back the kernel across
        the ino64 upgrade. Complicated use cases may not work properly, though
        enough simpler ones work to allow recovery in most situations.

20170620:
        Switch back to the BSDL dtc (Device Tree Compiler). Set WITH_GPL_DTC
        if you require the GPL compiler.

20170618:
        The internal ABI used for communication between the NFS kernel modules
        was changed by r320085, so __FreeBSD_version was bumped to
        ensure all the NFS related modules are updated together.

20170617:
        The ABI of struct event was changed by extending the data
        member to 64bit and adding ext fields.  For upgrade, same
        precautions as for the entry 20170523 "ino64" must be
        followed.

20170531:
        The GNU roff toolchain has been removed from base. To render manpages
        which are not supported by mandoc(1), man(1) can fallback on GNU roff
        from ports (and recommends to install it).
        To render roff(7) documents, consider using GNU roff from ports or the
        heirloom doctools roff toolchain from ports via pkg install groff or
        via pkg install heirloom-doctools.

20170524:
        The ath(4) and ath_hal(4) modules now build piecemeal to allow for
        smaller runtime footprint builds.  This is useful for embedded systems
        which only require one chipset support.

        If you load it as a module, make sure this is in /boot/loader.conf:

        if_ath_load="YES"

        This will load the HAL, all chip/RF backends and if_ath_pci.
        If you have if_ath_pci in /boot/loader.conf, ensure it is after
        if_ath or it will not load any HAL chipset support.

        If you want to selectively load things (eg on ye cheape ARM/MIPS
        platforms where RAM is at a premium) you should:

        * load ath_hal
        * load the chip modules in question
        * load ath_rate, ath_dfs
        * load ath_main
        * load if_ath_pci and/or if_ath_ahb depending upon your particular
          bus bind type - this is where probe/attach is done.

        For further comments/feedback, poke adrian@ .

20170523:
        The "ino64" 64-bit inode project has been committed, which extends
        a number of types to 64 bits.  Upgrading in place requires care and
        adherence to the documented upgrade procedure.

        If using a custom kernel configuration ensure that the
        COMPAT_FREEBSD11 option is included (as during the upgrade the
        system will be running the ino64 kernel with the existing world).

        For the safest in-place upgrade begin by removing previous build
        artifacts via "rm -rf /usr/obj/*".  Then, carefully follow the full
        procedure documented below under the heading "To rebuild everything and
        install it on the current system."  Specifically, a reboot is required
        after installing the new kernel before installing world. While an
        installworld normally works by accident from multiuser after rebooting
        the proper kernel, there are many cases where this will fail across this
        upgrade and installworld from single user is required.

20170424:
        The NATM framework including the en(4), fatm(4), hatm(4), and
        patm(4) devices has been removed.  Consumers should plan a
        migration before the end-of-life date for FreeBSD 11.

20170420:
        GNU diff has been replaced by a BSD licensed diff. Some features of GNU
        diff has not been implemented, if those are needed a newer version of
        GNU diff is available via the diffutils package under the gdiff name.

20170413:
        As of r316810 for ipfilter, keep frags is no longer assumed when
        keep state is specified in a rule. r316810 aligns ipfilter with
        documentation in man pages separating keep frags from keep state.
        This allows keep state to be specified without forcing keep frags
        and allows keep frags to be specified independently of keep state.
        To maintain previous behaviour, also specify keep frags with
        keep state (as documented in ipf.conf.5).

20170407:
        arm64 builds now use the base system LLD 4.0.0 linker by default,
        instead of requiring that the aarch64-binutils port or package be
        installed. To continue using aarch64-binutils, set
        CROSS_BINUTILS_PREFIX=/usr/local/aarch64-freebsd/bin .

20170405:
        The UDP optimization in entry 20160818 that added the sysctl
        net.inet.udp.require_l2_bcast has been reverted.  L2 broadcast
        packets will no longer be treated as L3 broadcast packets.

20170331:
        Binds and sends to the loopback addresses, IPv6 and IPv4, will now
        use any explicitly assigned loopback address available in the jail
        instead of using the first assigned address of the jail.

20170329:
        The ctl.ko module no longer implements the iSCSI target frontend:
        cfiscsi.ko does instead.

        If building cfiscsi.ko as a kernel module, the module can be loaded
        via one of the following methods:
        - `cfiscsi_load="YES"` in loader.conf(5).
        - Add `cfiscsi` to `$kld_list` in rc.conf(5).
        - ctladm(8)/ctld(8), when compiled with iSCSI support
          (`WITH_ISCSI=yes` in src.conf(5))

        Please see cfiscsi(4) for more details.

20170316:
        The mmcsd.ko module now additionally depends on geom_flashmap.ko.
        Also, mmc.ko and mmcsd.ko need to be a matching pair built from the
        same source (previously, the dependency of mmcsd.ko on mmc.ko was
        missing, but mmcsd.ko now will refuse to load if it is incompatible
        with mmc.ko).

20170315:
        The syntax of ipfw(8) named states was changed to avoid ambiguity.
        If you have used named states in the firewall rules, you need to modify
        them after installworld and before rebooting. Now named states must
        be prefixed with colon.

20170311:
        The old drm (sys/dev/drm/) drivers for i915 and radeon have been
        removed as the userland we provide cannot use them. The KMS version
        (sys/dev/drm2) supports the same hardware.

20170302:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 4.0.0.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20170221:
        The code that provides support for ZFS .zfs/ directory functionality
        has been reimplemented.  It's not possible now to create a snapshot
        by mkdir under .zfs/snapshot/.  That should be the only user visible
        change.

20170216:
        EISA bus support has been removed. The WITH_EISA option is no longer
        valid.

20170215:
        MCA bus support has been removed.

20170127:
        The WITH_LLD_AS_LD / WITHOUT_LLD_AS_LD build knobs have been renamed
        WITH_LLD_IS_LD / WITHOUT_LLD_IS_LD, for consistency with CLANG_IS_CC.

20170112:
        The EM_MULTIQUEUE kernel configuration option is deprecated now that
        the em(4) driver conforms to iflib specifications.

20170109:
        The igb(4), em(4) and lem(4) ethernet drivers are now implemented via
        IFLIB.  If you have a custom kernel configuration that excludes em(4)
        but you use igb(4), you need to re-add em(4) to your custom
        configuration.

20161217:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 3.9.1.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20161124:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 3.9.0.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20161119:
        The layout of the pmap structure has changed for powerpc to put the pmap
        statistics at the front for all CPU variations.  libkvm(3) and all tools
        that link against it need to be recompiled.

20161030:
        isl(4) and cyapa(4) drivers now require a new driver,
        chromebook_platform(4), to work properly on Chromebook-class hardware.
        On other types of hardware the drivers may need to be configured using
        device hints.  Please see the corresponding manual pages for details.

20161017:
        The urtwn(4) driver was merged into rtwn(4) and now consists of
        rtwn(4) main module + rtwn_usb(4) and rtwn_pci(4) bus-specific
        parts.
        Also, firmware for RTL8188CE was renamed due to possible name
        conflict (rtwnrtl8192cU(B) -> rtwnrtl8192cE(B))

20161015:
        GNU rcs has been removed from base.  It is available as packages:
        - rcs: Latest GPLv3 GNU rcs version.
        - rcs57: Copy of the latest version of GNU rcs (GPLv2) before it was
        removed from base.

20161008:
        Use of the cc_cdg, cc_chd, cc_hd, or cc_vegas congestion control
        modules now requires that the kernel configuration contain the
        TCP_HHOOK option. (This option is included in the GENERIC kernel.)

20161003:
        The WITHOUT_ELFCOPY_AS_OBJCOPY src.conf(5) knob has been retired.
        ELF Tool Chain's elfcopy is always installed as /usr/bin/objcopy.

20160924:
        Relocatable object files with the extension of .So have been renamed
        to use an extension of .pico instead.  The purpose of this change is
        to avoid a name clash with shared libraries on case-insensitive file
        systems.  On those file systems, foo.So is the same file as foo.so.

20160918:
        GNU rcs has been turned off by default.  It can (temporarily) be built
        again by adding WITH_RCS knob in src.conf.
        Otherwise, GNU rcs is available from packages:
        - rcs: Latest GPLv3 GNU rcs version.
        - rcs57: Copy of the latest version of GNU rcs (GPLv2) from base.

20160918:
        The backup_uses_rcs functionality has been removed from rc.subr.

20160908:
        The queue(3) debugging macro, QUEUE_MACRO_DEBUG, has been split into
        two separate components, QUEUE_MACRO_DEBUG_TRACE and
        QUEUE_MACRO_DEBUG_TRASH.  Define both for the original
        QUEUE_MACRO_DEBUG behavior.

20160824:
        r304787 changed some ioctl interfaces between the iSCSI userspace
        programs and the kernel.  ctladm, ctld, iscsictl, and iscsid must be
        rebuilt to work with new kernels.  __FreeBSD_version has been bumped
        to 1200005.

20160818:
        The UDP receive code has been updated to only treat incoming UDP
        packets that were addressed to an L2 broadcast address as L3
        broadcast packets.  It is not expected that this will affect any
        standards-conforming UDP application.  The new behaviour can be
        disabled by setting the sysctl net.inet.udp.require_l2_bcast to
        0.

20160818:
        Remove the openbsd_poll system call.
        __FreeBSD_version has been bumped because of this.

20160708:
        The stable/11 branch has been created from head@r302406.

20160622:
        The libc stub for the pipe(2) system call has been replaced with
        a wrapper that calls the pipe2(2) system call and the pipe(2)
        system call is now only implemented by the kernels that include
        "options COMPAT_FREEBSD10" in their config file (this is the
        default).  Users should ensure that this option is enabled in
        their kernel or upgrade userspace to r302092 before upgrading their
        kernel.

20160527:
        CAM will now strip leading spaces from SCSI disks' serial numbers.
        This will affect users who create UFS filesystems on SCSI disks using
        those disk's diskid device nodes.  For example, if /etc/fstab
        previously contained a line like
        "/dev/diskid/DISK-%20%20%20%20%20%20%20ABCDEFG0123456", you should
        change it to "/dev/diskid/DISK-ABCDEFG0123456".  Users of geom
        transforms like gmirror may also be affected.  ZFS users should
        generally be fine.

20160523:
        The bitstring(3) API has been updated with new functionality and
        improved performance.  But it is binary-incompatible with the old API.
        Objects built with the new headers may not be linked against objects
        built with the old headers.

20160520:
        The brk and sbrk functions have been removed from libc on arm64.
        Binutils from ports has been updated to not link to these
        functions and should be updated to the latest version before
        installing a new libc.

20160517:
        The armv6 port now defaults to hard float ABI. Limited support
        for running both hardfloat and soft float on the same system
        is available using the libraries installed with -DWITH_LIBSOFT.
        This has only been tested as an upgrade path for installworld
        and packages may fail or need manual intervention to run. New
        packages will be needed.

        To update an existing self-hosted armv6hf system, you must add
        TARGET_ARCH=armv6 on the make command line for both the build
        and the install steps.

20160510:
        Kernel modules compiled outside of a kernel build now default to
        installing to /boot/modules instead of /boot/kernel.  Many kernel
        modules built this way (such as those in ports) already overrode
        KMODDIR explicitly to install into /boot/modules.  However,
        manually building and installing a module from /sys/modules will
        now install to /boot/modules instead of /boot/kernel.

20160414:
        The CAM I/O scheduler has been committed to the kernel. There should be
        no user visible impact. This does enable NCQ Trim on ada SSDs. While the
        list of known rogues that claim support for this but actually corrupt
        data is believed to be complete, be on the lookout for data
        corruption. The known rogue list is believed to be complete:

                o Crucial MX100, M550 drives with MU01 firmware.
                o Micron M510 and M550 drives with MU01 firmware.
                o Micron M500 prior to MU07 firmware
                o Samsung 830, 840, and 850 all firmwares
                o FCCT M500 all firmwares

        Crucial has firmware http://www.crucial.com/usa/en/support-ssd-firmware
        with working NCQ TRIM. For Micron branded drives, see your sales rep for
        updated firmware. Black listed drives will work correctly because these
        drives work correctly so long as no NCQ TRIMs are sent to them. Given
        this list is the same as found in Linux, it's believed there are no
        other rogues in the market place. All other models from the above
        vendors work.

        To be safe, if you are at all concerned, you can quirk each of your
        drives to prevent NCQ from being sent by setting:
                kern.cam.ada.X.quirks="0x2"
        in loader.conf. If the drive requires the 4k sector quirk, set the
        quirks entry to 0x3.

20160330:
        The FAST_DEPEND build option has been removed and its functionality is
        now the one true way.  The old mkdep(1) style of 'make depend' has
        been removed.  See 20160311 for further details.

20160317:
        Resource range types have grown from unsigned long to uintmax_t.  All
        drivers, and anything using libdevinfo, need to be recompiled.

20160311:
        WITH_FAST_DEPEND is now enabled by default for in-tree and out-of-tree
        builds.  It no longer runs mkdep(1) during 'make depend', and the
        'make depend' stage can safely be skipped now as it is auto ran
        when building 'make all' and will generate all SRCS and DPSRCS before
        building anything else.  Dependencies are gathered at compile time with
        -MF flags kept in separate .depend files per object file.  Users should
        run 'make cleandepend' once if using -DNO_CLEAN to clean out older
        stale .depend files.

20160306:
        On amd64, clang 3.8.0 can now insert sections of type AMD64_UNWIND into
        kernel modules.  Therefore, if you load any kernel modules at boot time,
        please install the boot loaders after you install the kernel, but before
        rebooting, e.g.:

        make buildworld
        make buildkernel KERNCONF=YOUR_KERNEL_HERE
        make installkernel KERNCONF=YOUR_KERNEL_HERE
        make -C sys/boot install
        <reboot in single user>

        Then follow the usual steps, described in the General Notes section,
        below.

20160305:
        Clang, llvm, lldb and compiler-rt have been upgraded to 3.8.0.  Please
        see the 20141231 entry below for information about prerequisites and
        upgrading, if you are not already using clang 3.5.0 or higher.

20160301:
        The AIO subsystem is now a standard part of the kernel.  The
        VFS_AIO kernel option and aio.ko kernel module have been removed.
        Due to stability concerns, asynchronous I/O requests are only
        permitted on sockets and raw disks by default.  To enable
        asynchronous I/O requests on all file types, set the
        vfs.aio.enable_unsafe sysctl to a non-zero value.

20160226:
        The ELF object manipulation tool objcopy is now provided by the
        ELF Tool Chain project rather than by GNU binutils. It should be a
        drop-in replacement, with the addition of arm64 support. The
        (temporary) src.conf knob WITHOUT_ELFCOPY_AS_OBJCOPY knob may be set
        to obtain the GNU version if necessary.

20160129:
        Building ZFS pools on top of zvols is prohibited by default.  That
        feature has never worked safely; it's always been prone to deadlocks.
        Using a zvol as the backing store for a VM guest's virtual disk will
        still work, even if the guest is using ZFS.  Legacy behavior can be
        restored by setting vfs.zfs.vol.recursive=1.

20160119:
        The NONE and HPN patches has been removed from OpenSSH.  They are
        still available in the security/openssh-portable port.

20160113:
        With the addition of ypldap(8), a new _ypldap user is now required
        during installworld. "mergemaster -p" can be used to add the user
        prior to installworld, as documented in the handbook.

20151216:
        The tftp loader (pxeboot) now uses the option root-path directive. As a
        consequence it no longer looks for a pxeboot.4th file on the tftp
        server. Instead it uses the regular /boot infrastructure as with the
        other loaders.

20151211:
        The code to start recording plug and play data into the modules has
        been committed. While the old tools will properly build a new kernel,
        a number of warnings about "unknown metadata record 4" will be produced
        for an older kldxref. To avoid such warnings, make sure to rebuild
        the kernel toolchain (or world). Make sure that you have r292078 or
        later when trying to build 292077 or later before rebuilding.

20151207:
        Debug data files are now built by default with 'make buildworld' and
        installed with 'make installworld'. This facilitates debugging but
        requires more disk space both during the build and for the installed
        world. Debug files may be disabled by setting WITHOUT_DEBUG_FILES=yes
        in src.conf(5).

20151130:
        r291527 changed the internal interface between the nfsd.ko and
        nfscommon.ko modules. As such, they must both be upgraded to-gether.
        __FreeBSD_version has been bumped because of this.

20151108:
        Add support for unicode collation strings leads to a change of
        order of files listed by ls(1) for example. To get back to the old
        behaviour, set LC_COLLATE environment variable to "C".

        Databases administrators will need to reindex their databases given
        collation results will be different.

        Due to a bug in install(1) it is recommended to remove the ancient
        locales before running make installworld.

        rm -rf /usr/share/locale/*

20151030:
        The OpenSSL has been upgraded to 1.0.2d.  Any binaries requiring
        libcrypto.so.7 or libssl.so.7 must be recompiled.

20151020:
        Qlogic 24xx/25xx firmware images were updated from 5.5.0 to 7.3.0.
        Kernel modules isp_2400_multi and isp_2500_multi were removed and
        should be replaced with isp_2400 and isp_2500 modules respectively.

20151017:
        The build previously allowed using 'make -n' to not recurse into
        sub-directories while showing what commands would be executed, and
        'make -n -n' to recursively show commands.  Now 'make -n' will recurse
        and 'make -N' will not.

20151012:
        If you specify SENDMAIL_MC or SENDMAIL_CF in make.conf, mergemaster
        and etcupdate will now use this file. A custom sendmail.cf is now
        updated via this mechanism rather than via installworld.  If you had
        excluded sendmail.cf in mergemaster.rc or etcupdate.conf, you may
        want to remove the exclusion or change it to "always install".
        /etc/mail/sendmail.cf is now managed the same way regardless of
        whether SENDMAIL_MC/SENDMAIL_CF is used.  If you are not using
        SENDMAIL_MC/SENDMAIL_CF there should be no change in behavior.

20151011:
        Compatibility shims for legacy ATA device names have been removed.
        It includes ATA_STATIC_ID kernel option, kern.cam.ada.legacy_aliases
        and kern.geom.raid.legacy_aliases loader tunables, kern.devalias.*
        environment variables, /dev/ad* and /dev/ar* symbolic links.

20151006:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 3.7.0.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20150924:
        Kernel debug files have been moved to /usr/lib/debug/boot/kernel/,
        and renamed from .symbols to .debug. This reduces the size requirements
        on the boot partition or file system and provides consistency with
        userland debug files.

        When using the supported kernel installation method the
        /usr/lib/debug/boot/kernel directory will be renamed (to kernel.old)
        as is done with /boot/kernel.

        Developers wishing to maintain the historical behavior of installing
        debug files in /boot/kernel/ can set KERN_DEBUGDIR="" in src.conf(5).

20150827:
        The wireless drivers had undergone changes that remove the 'parent
        interface' from the ifconfig -l output. The rc.d network scripts
        used to check presence of a parent interface in the list, so old
        scripts would fail to start wireless networking. Thus, etcupdate(3)
        or mergemaster(8) run is required after kernel update, to update your
        rc.d scripts in /etc.

20150827:
        pf no longer supports 'scrub fragment crop' or 'scrub fragment drop-ovl'
        These configurations are now automatically interpreted as
        'scrub fragment reassemble'.

20150817:
        Kernel-loadable modules for the random(4) device are back. To use
        them, the kernel must have

        device  random
        options RANDOM_LOADABLE

        kldload(8) can then be used to load random_fortuna.ko
        or random_yarrow.ko. Please note that due to the indirect
        function calls that the loadable modules need to provide,
        the build-in variants will be slightly more efficient.

        The random(4) kernel option RANDOM_DUMMY has been retired due to
        unpopularity. It was not all that useful anyway.

20150813:
        The WITHOUT_ELFTOOLCHAIN_TOOLS src.conf(5) knob has been retired.
        Control over building the ELF Tool Chain tools is now provided by
        the WITHOUT_TOOLCHAIN knob.

20150810:
        The polarity of Pulse Per Second (PPS) capture events with the
        uart(4) driver has been corrected.  Prior to this change the PPS
        "assert" event corresponded to the trailing edge of a positive PPS
        pulse and the "clear" event was the leading edge of the next pulse.

        As the width of a PPS pulse in a typical GPS receiver is on the
        order of 1 millisecond, most users will not notice any significant
        difference with this change.

        Anyone who has compensated for the historical polarity reversal by
        configuring a negative offset equal to the pulse width will need to
        remove that workaround.

20150809:
        The default group assigned to /dev/dri entries has been changed
        from 'wheel' to 'video' with the id of '44'. If you want to have
        access to the dri devices please add yourself to the video group
        with:

        # pw groupmod video -m $USER

20150806:
        The menu.rc and loader.rc files will now be replaced during
        upgrades. Please migrate local changes to menu.rc.local and
        loader.rc.local instead.

20150805:
        GNU Binutils versions of addr2line, c++filt, nm, readelf, size,
        strings and strip have been removed. The src.conf(5) knob
        WITHOUT_ELFTOOLCHAIN_TOOLS no longer provides the binutils tools.

20150728:
        As ZFS requires more kernel stack pages than is the default on some
        architectures e.g. i386, it now warns if KSTACK_PAGES is less than
        ZFS_MIN_KSTACK_PAGES (which is 4 at the time of writing).

        Please consider using 'options KSTACK_PAGES=X' where X is greater
        than or equal to ZFS_MIN_KSTACK_PAGES i.e. 4 in such configurations.

20150706:
        sendmail has been updated to 8.15.2.  Starting with FreeBSD 11.0
        and sendmail 8.15, sendmail uses uncompressed IPv6 addresses by
        default, i.e., they will not contain "::".  For example, instead
        of ::1, it will be 0:0:0:0:0:0:0:1.  This permits a zero subnet
        to have a more specific match, such as different map entries for
        IPv6:0:0 vs IPv6:0.  This change requires that configuration
        data (including maps, files, classes, custom ruleset, etc.) must
        use the same format, so make certain such configuration data is
        upgrading.  As a very simple check search for patterns like
        'IPv6:[0-9a-fA-F:]*::' and 'IPv6::'.  To return to the old
        behavior, set the m4 option confUSE_COMPRESSED_IPV6_ADDRESSES or
        the cf option UseCompressedIPv6Addresses.

20150630:
        The default kernel entropy-processing algorithm is now
        Fortuna, replacing Yarrow.

        Assuming you have 'device random' in your kernel config
        file, the configurations allow a kernel option to override
        this default. You may choose *ONE* of:

        options RANDOM_YARROW   # Legacy /dev/random algorithm.
        options RANDOM_DUMMY    # Blocking-only driver.

        If you have neither, you get Fortuna.  For most people,
        read no further, Fortuna will give a /dev/random that works
        like it always used to, and the difference will be irrelevant.

        If you remove 'device random', you get *NO* kernel-processed
        entropy at all. This may be acceptable to folks building
        embedded systems, but has complications. Carry on reading,
        and it is assumed you know what you need.

        *PLEASE* read random(4) and random(9) if you are in the
        habit of tweaking kernel configs, and/or if you are a member
        of the embedded community, wanting specific and not-usual
        behaviour from your security subsystems.

        NOTE!! If you use RANDOM_DUMMY and/or have no 'device
        random', you will NOT have a functioning /dev/random, and
        many cryptographic features will not work, including SSH.
        You may also find strange behaviour from the random(3) set
        of library functions, in particular sranddev(3), srandomdev(3)
        and arc4random(3). The reason for this is that the KERN_ARND
        sysctl only returns entropy if it thinks it has some to
        share, and with RANDOM_DUMMY or no 'device random' this
        will never happen.

20150623:
        An additional fix for the issue described in the 20150614 sendmail
        entry below has been committed in revision 284717.

20150616:
        FreeBSD's old make (fmake) has been removed from the system. It is
        available as the devel/fmake port or via pkg install fmake.

20150615:
        The fix for the issue described in the 20150614 sendmail entry
        below has been committed in revision 284436.  The work
        around described in that entry is no longer needed unless the
        default setting is overridden by a confDH_PARAMETERS configuration
        setting of '5' or pointing to a 512 bit DH parameter file.

20150614:
        ALLOW_DEPRECATED_ATF_TOOLS/ATFFILE support has been removed from
        atf.test.mk (included from bsd.test.mk). Please upgrade devel/atf
        and devel/kyua to version 0.20+ and adjust any calling code to work
        with Kyuafile and kyua.

20150614:
        The import of openssl to address the FreeBSD-SA-15:10.openssl
        security advisory includes a change which rejects handshakes
        with DH parameters below 768 bits.  sendmail releases prior
        to 8.15.2 (not yet released), defaulted to a 512 bit
        DH parameter setting for client connections.  To work around
        this interoperability, sendmail can be configured to use a
        2048 bit DH parameter by:

        1. Edit /etc/mail/`hostname`.mc
        2. If a setting for confDH_PARAMETERS does not exist or
           exists and is set to a string beginning with '5',
           replace it with '2'.
        3. If a setting for confDH_PARAMETERS exists and is set to
           a file path, create a new file with:
                openssl dhparam -out /path/to/file 2048
        4. Rebuild the .cf file:
                cd /etc/mail/; make; make install
        5. Restart sendmail:
                cd /etc/mail/; make restart

        A sendmail patch is coming, at which time this file will be
        updated.

20150604:
        Generation of legacy formatted entries have been disabled by default
        in pwd_mkdb(8), as all base system consumers of the legacy formatted
        entries were converted to use the new format by default when the new,
        machine independent format have been added and supported since FreeBSD
        5.x.

        Please see the pwd_mkdb(8) manual page for further details.

20150525:
        Clang and llvm have been upgraded to 3.6.1 release.  Please see the
        20141231 entry below for information about prerequisites and upgrading,
        if you are not already using 3.5.0 or higher.

20150521:
        TI platform code switched to using vendor DTS files and this update
        may break existing systems running on Beaglebone, Beaglebone Black,
        and Pandaboard:

        - dtb files should be regenerated/reinstalled. Filenames are the
          same but content is different now
        - GPIO addressing was changed, now each GPIO bank (32 pins per bank)
          has its own /dev/gpiocX device, e.g. pin 121 on /dev/gpioc0 in old
          addressing scheme is now pin 25 on /dev/gpioc3.
        - Pandaboard: /etc/ttys should be updated, serial console device is
          now /dev/ttyu2, not /dev/ttyu0

20150501:
        soelim(1) from gnu/usr.bin/groff has been replaced by usr.bin/soelim.
        If you need the GNU extension from groff soelim(1), install groff
        from package: pkg install groff, or via ports: textproc/groff.

20150423:
        chmod, chflags, chown and chgrp now affect symlinks in -R mode as
        defined in symlink(7); previously symlinks were silently ignored.

20150415:
        The const qualifier has been removed from iconv(3) to comply with
        POSIX.  The ports tree is aware of this from r384038 onwards.

20150416:
        Libraries specified by LIBADD in Makefiles must have a corresponding
        DPADD_<lib> variable to ensure correct dependencies.  This is now
        enforced in src.libnames.mk.

20150324:
        From legacy ata(4) driver was removed support for SATA controllers
        supported by more functional drivers ahci(4), siis(4) and mvs(4).
        Kernel modules ataahci and ataadaptec were removed completely,
        replaced by ahci and mvs modules respectively.

20150315:
        Clang, llvm and lldb have been upgraded to 3.6.0 release.  Please see
        the 20141231 entry below for information about prerequisites and
        upgrading, if you are not already using 3.5.0 or higher.

20150307:
        The 32-bit PowerPC kernel has been changed to a position-independent
        executable. This can only be booted with a version of loader(8)
        newer than January 31, 2015, so make sure to update both world and
        kernel before rebooting.

20150217:
        If you are running a -CURRENT kernel since r273872 (Oct 30th, 2014),
        but before r278950, the RNG was not seeded properly.  Immediately
        upgrade the kernel to r278950 or later and regenerate any keys (e.g.
        ssh keys or openssl keys) that were generated w/ a kernel from that
        range.  This does not affect programs that directly used /dev/random
        or /dev/urandom.  All userland uses of arc4random(3) are affected.

20150210:
        The autofs(4) ABI was changed in order to restore binary compatibility
        with 10.1-RELEASE.  The automountd(8) daemon needs to be rebuilt to work
        with the new kernel.

20150131:
        The powerpc64 kernel has been changed to a position-independent
        executable. This can only be booted with a new version of loader(8),
        so make sure to update both world and kernel before rebooting.

20150118:
        Clang and llvm have been upgraded to 3.5.1 release.  This is a bugfix
        only release, no new features have been added.  Please see the 20141231
        entry below for information about prerequisites and upgrading, if you
        are not already using 3.5.0.

20150107:
        ELF tools addr2line, elfcopy (strip), nm, size, and strings are now
        taken from the ELF Tool Chain project rather than GNU binutils. They
        should be drop-in replacements, with the addition of arm64 support.
        The WITHOUT_ELFTOOLCHAIN_TOOLS= knob may be used to obtain the
        binutils tools, if necessary. See 20150805 for updated information.

20150105:
        The default Unbound configuration now enables remote control
        using a local socket.  Users who have already enabled the
        local_unbound service should regenerate their configuration
        by running "service local_unbound setup" as root.

20150102:
        The GNU texinfo and GNU info pages have been removed.
        To be able to view GNU info pages please install texinfo from ports.

20141231:
        Clang, llvm and lldb have been upgraded to 3.5.0 release.

        As of this release, a prerequisite for building clang, llvm and lldb is
        a C++11 capable compiler and C++11 standard library.  This means that to
        be able to successfully build the cross-tools stage of buildworld, with
        clang as the bootstrap compiler, your system compiler or cross compiler
        should either be clang 3.3 or later, or gcc 4.8 or later, and your
        system C++ library should be libc++, or libdstdc++ from gcc 4.8 or
        later.

        On any standard FreeBSD 10.x or 11.x installation, where clang and
        libc++ are on by default (that is, on x86 or arm), this should work out
        of the box.

        On 9.x installations where clang is enabled by default, e.g. on x86 and
        powerpc, libc++ will not be enabled by default, so libc++ should be
        built (with clang) and installed first.  If both clang and libc++ are
        missing, build clang first, then use it to build libc++.

        On 8.x and earlier installations, upgrade to 9.x first, and then follow
        the instructions for 9.x above.

        Sparc64 and mips users are unaffected, as they still use gcc 4.2.1 by
        default, and do not build clang.

        Many embedded systems are resource constrained, and will not be able to
        build clang in a reasonable time, or in some cases at all.  In those
        cases, cross building bootable systems on amd64 is a workaround.

        This new version of clang introduces a number of new warnings, of which
        the following are most likely to appear:

        -Wabsolute-value

        This warns in two cases, for both C and C++:
        * When the code is trying to take the absolute value of an unsigned
          quantity, which is effectively a no-op, and almost never what was
          intended.  The code should be fixed, if at all possible.  If you are
          sure that the unsigned quantity can be safely cast to signed, without
          loss of information or undefined behavior, you can add an explicit
          cast, or disable the warning.

        * When the code is trying to take an absolute value, but the called
          abs() variant is for the wrong type, which can lead to truncation.
          If you want to disable the warning instead of fixing the code, please
          make sure that truncation will not occur, or it might lead to unwanted
          side-effects.

        -Wtautological-undefined-compare and
        -Wundefined-bool-conversion

        These warn when C++ code is trying to compare 'this' against NULL, while
        'this' should never be NULL in well-defined C++ code.  However, there is
        some legacy (pre C++11) code out there, which actively abuses this
        feature, which was less strictly defined in previous C++ versions.

        Squid and openjdk do this, for example.  The warning can be turned off
        for C++98 and earlier, but compiling the code in C++11 mode might result
        in unexpected behavior; for example, the parts of the program that are
        unreachable could be optimized away.

20141222:
        The old NFS client and server (kernel options NFSCLIENT, NFSSERVER)
        kernel sources have been removed. The .h files remain, since some
        utilities include them. This will need to be fixed later.
        If "mount -t oldnfs ..." is attempted, it will fail.
        If the "-o" option on mountd(8), nfsd(8) or nfsstat(1) is used,
        the utilities will report errors.

20141121:
        The handling of LOCAL_LIB_DIRS has been altered to skip addition of
        directories to top level SUBDIR variable when their parent
        directory is included in LOCAL_DIRS.  Users with build systems with
        such hierarchies and without SUBDIR entries in the parent
        directory Makefiles should add them or add the directories to
        LOCAL_DIRS.

20141109:
        faith(4) and faithd(8) have been removed from the base system. Faith
        has been obsolete for a very long time.

20141104:
        vt(4), the new console driver, is enabled by default. It brings
        support for Unicode and double-width characters, as well as
        support for UEFI and integration with the KMS kernel video
        drivers.

        You may need to update your console settings in /etc/rc.conf,
        most probably the keymap. During boot, /etc/rc.d/syscons will
        indicate what you need to do.

        vt(4) still has issues and lacks some features compared to
        syscons(4). See the wiki for up-to-date information:
          https://wiki.freebsd.org/Newcons

        If you want to keep using syscons(4), you can do so by adding
        the following line to /boot/loader.conf:
          kern.vty=sc

20141102:
        pjdfstest has been integrated into kyua as an opt-in test suite.
        Please see share/doc/pjdfstest/README for more details on how to
        execute it.

20141009:
        gperf has been removed from the base system for architectures
        that use clang. Ports that require gperf will obtain it from the
        devel/gperf port.

20140923:
        pjdfstest has been moved from tools/regression/pjdfstest to
        contrib/pjdfstest .

20140922:
        At svn r271982, The default linux compat kernel ABI has been adjusted
        to 2.6.18 in support of the linux-c6 compat ports infrastructure
        update.  If you wish to continue using the linux-f10 compat ports,
        add compat.linux.osrelease=2.6.16 to your local sysctl.conf.  Users are
        encouraged to update their linux-compat packages to linux-c6 during
        their next update cycle.

20140729:
        The ofwfb driver, used to provide a graphics console on PowerPC when
        using vt(4), no longer allows mmap() of all physical memory. This
        will prevent Xorg on PowerPC with some ATI graphics cards from
        initializing properly unless x11-servers/xorg-server is updated to
        1.12.4_8 or newer.

20140723:
        The xdev targets have been converted to using TARGET and
        TARGET_ARCH instead of XDEV and XDEV_ARCH.

20140719:
        The default unbound configuration has been modified to address
        issues with reverse lookups on networks that use private
        address ranges.  If you use the local_unbound service, run
        "service local_unbound setup" as root to regenerate your
        configuration, then "service local_unbound reload" to load the
        new configuration.

20140709:
        The GNU texinfo and GNU info pages are not built and installed
        anymore, WITH_INFO knob has been added to allow to built and install
        them again.
        UPDATE: see 20150102 entry on texinfo's removal

20140708:
        The GNU readline library is now an INTERNALLIB - that is, it is
        statically linked into consumers (GDB and variants) in the base
        system, and the shared library is no longer installed.  The
        devel/readline port is available for third party software that
        requires readline.

20140702:
        The Itanium architecture (ia64) has been removed from the list of
        known architectures. This is the first step in the removal of the
        architecture.

20140701:
        Commit r268115 has added NFSv4.1 server support, merged from
        projects/nfsv4.1-server.  Since this includes changes to the
        internal interfaces between the NFS related modules, a full
        build of the kernel and modules will be necessary.
        __FreeBSD_version has been bumped.

20140629:
        The WITHOUT_VT_SUPPORT kernel config knob has been renamed
        WITHOUT_VT.  (The other _SUPPORT knobs have a consistent meaning
        which differs from the behaviour controlled by this knob.)

20140619:
        Maximal length of the serial number in CTL was increased from 16 to
        64 chars, that breaks ABI.  All CTL-related tools, such as ctladm
        and ctld, need to be rebuilt to work with a new kernel.

20140606:
        The libatf-c and libatf-c++ major versions were downgraded to 0 and
        1 respectively to match the upstream numbers.  They were out of
        sync because, when they were originally added to FreeBSD, the
        upstream versions were not respected.  These libraries are private
        and not yet built by default, so renumbering them should be a
        non-issue.  However, unclean source trees will yield broken test
        programs once the operator executes "make delete-old-libs" after a
        "make installworld".

        Additionally, the atf-sh binary was made private by moving it into
        /usr/libexec/.  Already-built shell test programs will keep the
        path to the old binary so they will break after "make delete-old"
        is run.

        If you are using WITH_TESTS=yes (not the default), wipe the object
        tree and rebuild from scratch to prevent spurious test failures.
        This is only needed once: the misnumbered libraries and misplaced
        binaries have been added to OptionalObsoleteFiles.inc so they will
        be removed during a clean upgrade.

20140512:
        Clang and llvm have been upgraded to 3.4.1 release.

20140508:
        We bogusly installed src.opts.mk in /usr/share/mk. This file should
        be removed to avoid issues in the future (and has been added to
        ObsoleteFiles.inc).

20140505:
        /etc/src.conf now affects only builds of the FreeBSD src tree. In the
        past, it affected all builds that used the bsd.*.mk files. The old
        behavior was a bug, but people may have relied upon it. To get this
        behavior back, you can .include /etc/src.conf from /etc/make.conf
        (which is still global and isn't changed). This also changes the
        behavior of incremental builds inside the tree of individual
        directories. Set MAKESYSPATH to ".../share/mk" to do that.
        Although this has survived make universe and some upgrade scenarios,
        other upgrade scenarios may have broken. At least one form of
        temporary breakage was fixed with MAKESYSPATH settings for buildworld
        as well... In cases where MAKESYSPATH isn't working with this
        setting, you'll need to set it to the full path to your tree.

        One side effect of all this cleaning up is that bsd.compiler.mk
        is no longer implicitly included by bsd.own.mk. If you wish to
        use COMPILER_TYPE, you must now explicitly include bsd.compiler.mk
        as well.

20140430:
        The lindev device has been removed since /dev/full has been made a
        standard device.  __FreeBSD_version has been bumped.

20140424:
        The knob WITHOUT_VI was added to the base system, which controls
        building ex(1), vi(1), etc. Older releases of FreeBSD required ex(1)
        in order to reorder files share/termcap and didn't build ex(1) as a
        build tool, so building/installing with WITH_VI is highly advised for
        build hosts for older releases.

        This issue has been fixed in stable/9 and stable/10 in r277022 and
        r276991, respectively.

20140418:
        The YES_HESIOD knob has been removed. It has been obsolete for
        a decade. Please move to using WITH_HESIOD instead or your builds
        will silently lack HESIOD.

20140405:
        The uart(4) driver has been changed with respect to its handling
        of the low-level console. Previously the uart(4) driver prevented
        any process from changing the baudrate or the CLOCAL and HUPCL
        control flags. By removing the restrictions, operators can make
        changes to the serial console port without having to reboot.
        However, when getty(8) is started on the serial device that is
        associated with the low-level console, a misconfigured terminal
        line in /etc/ttys will now have a real impact.
        Before upgrading the kernel, make sure that /etc/ttys has the
        serial console device configured as 3wire without baudrate to
        preserve the previous behaviour. E.g:
            ttyu0  "/usr/libexec/getty 3wire"  vt100  on  secure

20140306:
        Support for libwrap (TCP wrappers) in rpcbind was disabled by default
        to improve performance.  To re-enable it, if needed, run rpcbind
        with command line option -W.

20140226:
        Switched back to the GPL dtc compiler due to updates in the upstream
        dts files not being supported by the BSDL dtc compiler. You will need
        to rebuild your kernel toolchain to pick up the new compiler. Core dumps
        may result while building dtb files during a kernel build if you fail
        to do so. Set WITHOUT_GPL_DTC if you require the BSDL compiler.

20140216:
        Clang and llvm have been upgraded to 3.4 release.

20140216:
        The nve(4) driver has been removed.  Please use the nfe(4) driver
        for NVIDIA nForce MCP Ethernet adapters instead.

20140212:
        An ABI incompatibility crept into the libc++ 3.4 import in r261283.
        This could cause certain C++ applications using shared libraries built
        against the previous version of libc++ to crash.  The incompatibility
        has now been fixed, but any C++ applications or shared libraries built
        between r261283 and r261801 should be recompiled.

20140204:
        OpenSSH will now ignore errors caused by kernel lacking of Capsicum
        capability mode support.  Please note that enabling the feature in
        kernel is still highly recommended.

20140131:
        OpenSSH is now built with sandbox support, and will use sandbox as
        the default privilege separation method.  This requires Capsicum
        capability mode support in kernel.

20140128:
        The libelf and libdwarf libraries have been updated to newer
        versions from upstream. Shared library version numbers for
        these two libraries were bumped. Any ports or binaries
        requiring these two libraries should be recompiled.
        __FreeBSD_version is bumped to 1100006.

20140110:
        If a Makefile in a tests/ directory was auto-generating a Kyuafile
        instead of providing an explicit one, this would prevent such
        Makefile from providing its own Kyuafile in the future during
        NO_CLEAN builds.  This has been fixed in the Makefiles but manual
        intervention is needed to clean an objdir if you use NO_CLEAN:
          # find /usr/obj -name Kyuafile | xargs rm -f

20131213:
        The behavior of gss_pseudo_random() for the krb5 mechanism
        has changed, for applications requesting a longer random string
        than produced by the underlying enctype's pseudo-random() function.
        In particular, the random string produced from a session key of
        enctype aes256-cts-hmac-sha1-96 or aes256-cts-hmac-sha1-96 will
        be different at the 17th octet and later, after this change.
        The counter used in the PRF+ construction is now encoded as a
        big-endian integer in accordance with RFC 4402.
        __FreeBSD_version is bumped to 1100004.

20131108:
        The WITHOUT_ATF build knob has been removed and its functionality
        has been subsumed into the more generic WITHOUT_TESTS.  If you were
        using the former to disable the build of the ATF libraries, you
        should change your settings to use the latter.

20131025:
        The default version of mtree is nmtree which is obtained from
        NetBSD.  The output is generally the same, but may vary
        slightly.  If you found you need identical output adding
        "-F freebsd9" to the command line should do the trick.  For the
        time being, the old mtree is available as fmtree.

20131014:
        libbsdyml has been renamed to libyaml and moved to /usr/lib/private.
        This will break ports-mgmt/pkg. Rebuild the port, or upgrade to pkg
        1.1.4_8 and verify bsdyml not linked in, before running "make
        delete-old-libs":
          # make -C /usr/ports/ports-mgmt/pkg build deinstall install clean
          or
          # pkg install pkg; ldd /usr/local/sbin/pkg | grep bsdyml

20131010:
        The stable/10 branch has been created in subversion from head
        revision r256279.

COMMON ITEMS:

        General Notes
        -------------
        Avoid using make -j when upgrading.  While generally safe, there are
        sometimes problems using -j to upgrade.  If your upgrade fails with
        -j, please try again without -j.  From time to time in the past there
        have been problems using -j with buildworld and/or installworld.  This
        is especially true when upgrading between "distant" versions (eg one
        that cross a major release boundary or several minor releases, or when
        several months have passed on the -current branch).

        Sometimes, obscure build problems are the result of environment
        poisoning.  This can happen because the make utility reads its
        environment when searching for values for global variables.  To run
        your build attempts in an "environmental clean room", prefix all make
        commands with 'env -i '.  See the env(1) manual page for more details.

        When upgrading from one major version to another it is generally best to
        upgrade to the latest code in the currently installed branch first, then
        do an upgrade to the new branch. This is the best-tested upgrade path,
        and has the highest probability of being successful.  Please try this
        approach if you encounter problems with a major version upgrade.  Since
        the stable 4.x branch point, one has generally been able to upgrade from
        anywhere in the most recent stable branch to head / current (or even the
        last couple of stable branches). See the top of this file when there's
        an exception.

        When upgrading a live system, having a root shell around before
        installing anything can help undo problems. Not having a root shell
        around can lead to problems if pam has changed too much from your
        starting point to allow continued authentication after the upgrade.

        This file should be read as a log of events. When a later event changes
        information of a prior event, the prior event should not be deleted.
        Instead, a pointer to the entry with the new information should be
        placed in the old entry. Readers of this file should also sanity check
        older entries before relying on them blindly. Authors of new entries
        should write them with this in mind.

        ZFS notes
        ---------
        When upgrading the boot ZFS pool to a new version, always follow
        these two steps:

        1.) recompile and reinstall the ZFS boot loader and boot block
        (this is part of "make buildworld" and "make installworld")

        2.) update the ZFS boot block on your boot drive

        The following example updates the ZFS boot block on the first
        partition (freebsd-boot) of a GPT partitioned drive ada0:
        "gpart bootcode -p /boot/gptzfsboot -i 1 ada0"

        Non-boot pools do not need these updates.

        To build a kernel
        -----------------
        If you are updating from a prior version of FreeBSD (even one just
        a few days old), you should follow this procedure.  It is the most
        failsafe as it uses a /usr/obj tree with a fresh mini-buildworld,

        make kernel-toolchain
        make -DALWAYS_CHECK_MAKE buildkernel KERNCONF=YOUR_KERNEL_HERE
        make -DALWAYS_CHECK_MAKE installkernel KERNCONF=YOUR_KERNEL_HERE

        To test a kernel once
        ---------------------
        If you just want to boot a kernel once (because you are not sure
        if it works, or if you want to boot a known bad kernel to provide
        debugging information) run
        make installkernel KERNCONF=YOUR_KERNEL_HERE KODIR=/boot/testkernel
        nextboot -k testkernel

        To rebuild everything and install it on the current system.
        -----------------------------------------------------------
        # Note: sometimes if you are running current you gotta do more than
        # is listed here if you are upgrading from a really old current.

        <make sure you have good level 0 dumps>
        make buildworld
        make buildkernel KERNCONF=YOUR_KERNEL_HERE
        make installkernel KERNCONF=YOUR_KERNEL_HERE
                                                        [1]
        <reboot in single user>                         [3]
        mergemaster -Fp                                 [5]
        make installworld
        mergemaster -Fi                                 [4]
        make delete-old                                 [6]
        <reboot>

        To cross-install current onto a separate partition
        --------------------------------------------------
        # In this approach we use a separate partition to hold
        # current's root, 'usr', and 'var' directories.   A partition
        # holding "/", "/usr" and "/var" should be about 2GB in
        # size.

        <make sure you have good level 0 dumps>
        <boot into -stable>
        make buildworld
        make buildkernel KERNCONF=YOUR_KERNEL_HERE
        <maybe newfs current's root partition>
        <mount current's root partition on directory ${CURRENT_ROOT}>
        make installworld DESTDIR=${CURRENT_ROOT} -DDB_FROM_SRC
        make distribution DESTDIR=${CURRENT_ROOT} # if newfs'd
        make installkernel KERNCONF=YOUR_KERNEL_HERE DESTDIR=${CURRENT_ROOT}
        cp /etc/fstab ${CURRENT_ROOT}/etc/fstab                    # if newfs'd
        <edit ${CURRENT_ROOT}/etc/fstab to mount "/" from the correct partition>
        <reboot into current>
        <do a "native" rebuild/install as described in the previous section>
        <maybe install compatibility libraries from ports/misc/compat*>
        <reboot>


        To upgrade in-place from stable to current
        ----------------------------------------------
        <make sure you have good level 0 dumps>
        make buildworld                                 [9]
        make buildkernel KERNCONF=YOUR_KERNEL_HERE      [8]
        make installkernel KERNCONF=YOUR_KERNEL_HERE
                                                        [1]
        <reboot in single user>                         [3]
        mergemaster -Fp                                 [5]
        make installworld
        mergemaster -Fi                                 [4]
        make delete-old                                 [6]
        <reboot>

        Make sure that you've read the UPDATING file to understand the
        tweaks to various things you need.  At this point in the life
        cycle of current, things change often and you are on your own
        to cope.  The defaults can also change, so please read ALL of
        the UPDATING entries.

        Also, if you are tracking -current, you must be subscribed to
        freebsd-current@freebsd.org.  Make sure that before you update
        your sources that you have read and understood all the recent
        messages there.  If in doubt, please track -stable which has
        much fewer pitfalls.

        [1] If you have third party modules, such as vmware, you
        should disable them at this point so they don't crash your
        system on reboot.

        [3] From the bootblocks, boot -s, and then do
                fsck -p
                mount -u /
                mount -a
                sh /etc/rc.d/zfs start  # mount zfs filesystem, if needed
                cd src                  # full path to source
                adjkerntz -i            # if CMOS is wall time
        Also, when doing a major release upgrade, it is required that
        you boot into single user mode to do the installworld.

        [4] Note: This step is non-optional.  Failure to do this step
        can result in a significant reduction in the functionality of the
        system.  Attempting to do it by hand is not recommended and those
        that pursue this avenue should read this file carefully, as well
        as the archives of freebsd-current and freebsd-hackers mailing lists
        for potential gotchas.  The -U option is also useful to consider.
        See mergemaster(8) for more information.

        [5] Usually this step is a no-op.  However, from time to time
        you may need to do this if you get unknown user in the following
        step.  It never hurts to do it all the time.  You may need to
        install a new mergemaster (cd src/usr.sbin/mergemaster && make
        install) after the buildworld before this step if you last updated
        from current before 20130425 or from -stable before 20130430.

        [6] This only deletes old files and directories. Old libraries
        can be deleted by "make delete-old-libs", but you have to make
        sure that no program is using those libraries anymore.

        [8] The new kernel must be able to run existing binaries used by an
        installworld.  When upgrading across major versions, the new kernel's
        configuration must include the correct COMPAT_FREEBSD<n> option for
        existing binaries (e.g. COMPAT_FREEBSD11 to run 11.x binaries).  Failure
        to do so may leave you with a system that is hard to boot to recover. A
        GENERIC kernel will include suitable compatibility options to run
        binaries from older branches.  Note that the ability to run binaries
        from unsupported branches is not guaranteed.

        Make sure that you merge any new devices from GENERIC since the
        last time you updated your kernel config file. Options also
        change over time, so you may need to adjust your custom kernels
        for these as well.

        [9] If CPUTYPE is defined in your /etc/make.conf, make sure to use the
        "?=" instead of the "=" assignment operator, so that buildworld can
        override the CPUTYPE if it needs to.

        MAKEOBJDIRPREFIX must be defined in an environment variable, and
        not on the command line, or in /etc/make.conf.  buildworld will
        warn if it is improperly defined.
FORMAT:

This file contains a list, in reverse chronological order, of major
breakages in tracking -current.  It is not guaranteed to be a complete
list of such breakages, and only contains entries since September 23, 2011.
If you need to see UPDATING entries from before that date, you will need
to fetch an UPDATING file from an older FreeBSD release.

Copyright information:

Copyright 1998-2009 M. Warner Losh.

Redistribution, publication, translation and use, with or without
modification, in full or in part, in any form or format of this
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THIS DOCUMENT IS PROVIDED BY WARNER LOSH ``AS IS'' AND ANY EXPRESS OR
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED.  IN NO EVENT SHALL WARNER LOSH BE LIABLE FOR ANY DIRECT,
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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$FreeBSD$